It has heretofore been proposed to measure the sidewall thickness of a glass container by placing the container on a mandrel arm with a pivoting head. The mandrel arm is inserted through the open mouth of the container. The head has a tip that internally engages the container sidewall, and is mechanically coupled to a second arm that carries an electronic gauge. The gauge has a tip that externally engages the container sidewall opposite the point of internal engagement between the head and the inside surface of the sidewall. The mechanical coupling between the arms is such that the arms may move up and down in unison to accommodate non-circularity of the container as it is manually rotated on the mandrel without affecting the output of the electronic gauge. However, if the sidewall thickness changes between the gauge tip and the head tip, a corresponding change is indicated at the gauge. The electronic gauge includes or is coupled to circuitry for storing maximum and minimum thickness signals as the container is rotated.
Although container sidewall measurement technique so described has been employed successfully in the art, further improvements remain desirable. For example, the described technique provides maximum and minimum thickness measurements, but does not provide any indication of angular orientation of either reading. Furthermore, although the gauge elements may be selectively positioned by an operator at any desired axial location along the container sidewall, three-dimensional profile measurements cannot be readily obtained. It is also not possible, employing the described technique, to obtain a thickness measurement at the heel of the container or the load-bearing surface because of the convex contour of the container bottom within the container. It is therefore a general object of the present invention to provide a method and apparatus for automatically obtaining two-dimensional or three-dimensional profile measurements of the wall thickness of containers such as glass bottles. Another and more specific object of the present invention is to provide a method and apparatus of the described character that are adapted to obtain thickness measurements not only at the sidewall of the container, but also at the container heel and load-bearing area around the periphery of the container bottom. Another object of the present invention is to provide a method and apparatus that satisfy the foregoing objectives, and that can be readily implemented in a manufacturing environment.